Hydrocyanation Catalyst Selectivity and Yield Optimization
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Solution Overview
Problem
The hydrocyanation of unactivated ethylenically unsaturated compounds, such as 3-pentenenitriles and 4-pentenenitriles, requires a Lewis acid promoter to achieve industrially useful rates and yields, but this process is hindered by isomerization issues, particularly the production of 2-pentenenitriles, which are detrimental to catalyst efficiency and yield losses.
Innovation Solution
A continuous process using a catalyst composition of zero-valent nickel combined with a bidentate phosphorus-containing ligand and a Lewis acid promoter, controlling the feed ratios of 2-pentenenitriles to all unsaturated nitriles and hydrogen cyanide to all unsaturated nitriles, and employing extraction and distillation steps to refine the reaction product mixture, thereby reducing 2-pentenenitrile concentrations and minimizing yield losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a Lewis acid promoter is used to achieve industrially useful rates and yields in hydrocyanation of unactivated ethylenically unsaturated compounds, then reaction rate and yield are improved, but isomerization to 2-pentenenitriles occurs which is detrimental to catalyst efficiency
Solution Approach 1:
The patent changes the chemical parameters of the catalyst system by using zero-valent nickel catalysts with multidentate phosphite ligands instead of conventional catalysts. This parameter change allows the reaction to proceed at useful rates without requiring Lewis acid promoters, thereby avoiding the harmful isomerization side reaction while maintaining productivity.
Solution Approach 2:
The multidentate phosphite ligands act as intermediaries that modify the catalyst's interaction with the substrate. These ligands create a more selective catalytic pathway that favors the desired hydrocyanation reaction over isomerization, effectively mediating between the need for reaction rate and the need to avoid harmful side reactions.
2Device complexity
If conventional catalyst systems are used for hydrocyanation, then the process is simpler, but 2-pentenenitriles are produced which cause yield losses and catalyst deactivation
Solution Approach 1:
The patent employs zero-valent nickel catalysts with multidentate phosphite ligands, changing the catalytic parameters to achieve high selectivity for the desired product. This parameter change eliminates the formation of 2-pentenenitriles, preventing yield losses and catalyst deactivation while maintaining process feasibility.
Solution Approach 2:
The patent uses a catalyst system that is highly selective and resistant to deactivation, effectively making the catalyst a durable, long-lasting component rather than a short-lived one. This approach reduces the need for frequent catalyst replacement and minimizes waste, aligning with sustainable manufacturing principles.
3Reliability
If 2-pentenenitriles are removed from the reaction mixture, then catalyst efficiency is maintained, but additional separation steps are required which increase process complexity
Solution Approach 1:
The patent converts the potential harm of 2-pentenenitrile formation into a benefit by using a catalyst system that is so selective that 2-pentenenitriles are not formed in the first place. This eliminates the need for separation steps to remove harmful byproducts, maintaining catalyst efficiency without adding process complexity.
Solution Approach 2:
The patent takes out the harmful isomerization step from the reaction pathway by using a selective catalyst system. This prevents the formation of 2-pentenenitriles at the source, eliminating the need for subsequent extraction or separation steps and simplifying the overall process.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly reduces yield losses due to 2-pentenenitrile production, maintains catalyst efficiency, and simplifies the adiponitrile manufacturing process by eliminating the need for dedicated separation columns and reducing investment and operating costs.
Implementation Method 1
a catalyst composition comprising a zero-valent nickel and at least one bidentate phosphorus-containing ligand
Implementation Method 2
requires the use of a Lewis acid promoter to obtain industrially useful rates and yields
Implementation Method 3
employing extraction and distillation steps to refine the reaction product mixture
Implementation Method 4
employing extraction and distillation steps to refine the reaction product mixture
Data Source
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AI summary
The invention provides a hydrocyanation process to produce adiponitrile and other dinitriles having six carbon atoms, the process comprising: a) forming a reaction mixture in the presence of at least one Lewis acid, said reaction mixture comprising ethylenically unsaturated nitriles having five carbon atoms, hydrogen cyanide, and at least one catalyst composition, by continuously feeding the ethylenically unsaturated nitriles, the hydrogen cyanide, and the catalyst composition; wherein the catalyst composition comprises a zero-valent nickel and at least one bidentate phosphorus-containing ligand; the bidentate phosphorus-containing ligand is selected from the group consisting of a phosphite, a phosphonite, a phosphinite, a phosphine, and a mixed phosphorus-containing ligand or a combination of such members; and the bidentate phosphorus-containing ligand gives acceptable results according to at least one protocol of the 2-Pentenenitrile Hydrocyanation Test Method; b) controlling X and Z, wherein X is the overall feed molar ratio of 2- pentenenitriles to all unsaturated nitriles; and Z is the overall feed molar ratio of hydrogen cyanide to all unsaturated nitriles; by selecting a value for X in the range of about 0.001 to about 0.5; and a value for Z in the range of about 0.5 to about 0.99; such that the value of quotient Q, wherein Formula (I), is in the range from about 0.2 to about 10, wherein 3PN is 3-pentenenitriles and 4PN is 4-pentenenitrile; c) withdrawing a reaction product mixture comprising adiponitrile, 2- methylglutaronitrile, ethylenically unsaturated nitriles, the catalyst composition, and catalyst composition degradation products; and wherein the ratio of the concentration of 2-pentenenitriles to the concentration of 3-pentenenitriles in the reaction mixture is in the range from about 0.2/1 to about 10/1; d) extracting at least a portion of the reaction product mixture with an extraction agent selected from the group consisting of aliphatic hydrocarbons, cycloaliphatic hydrocarbons, and mixtures thereof to obtain an extract phase comprising the extraction agent and the catalyst composition and a raffinate phase comprising adiponitrile, 2-methylglutaronitrile, ethylenically unsaturated nitriles, catalyst composition degradation products, and the extraction agent; and e) distilling the extract phase to obtain a first stream comprising the extraction agent and a second stream comprising the catalyst composition.